Apparatus for making spiral corrugations

ABSTRACT

Three tilted indenting members are used to form spiral corrugations in thin-walled metal tubes. The first indenting member starts the formation of the ridges and grooves. The second and third indenting members compress or pinch the previously formed ridges, resulting in a final corrugated tube having an outside diameter greater than the outside diameter of the tube originally fed into the corrugating machine.

United States Patent 1 Vaill 1 Mar. 12, 1974 APPARATUS FOR MAKING SPIRAL CORRUGATIONS [75] Inventor: John L. Vaill, Cheshire, Conn.

[73] Assignee: The Torrington Company,

Torrington, Conn.

[22] Filed: Oct. 30, 1972 [21] Appl. No.: 302,481

52.] US. Cl. 72'/77, 72/98 [51] Int. Cl B211) 13/20 [58] Field of Search 72/77, 78, 98

[5 6] References Cited UNITED STATES PATENTS 3,486,357 12/1969 Raisch 72/77 3,353,389 11/1967 Kelstrom 72/77 3,349,594 10/1967 Sporck ..72/78 1,554,739 9/1925 Lewis 72/77 3,583,189 6/1971 Kelstrom..... 3,572,074 3/1971 Holdup 1,919,254 7/1933 Picece et a1. 72/77 Primary Examiner-Charles W. Lanham Assistant Examiner.1ames R. Duzan Attorney, Agent, or Firm-Frank S. Troidl [57] ABSTRACT Three tilted indenting members are used to form spiral corrugations in thin-walled metal tubes. The first in- Y denting member starts the formation of the ridges and grooves. The second and third indenting members compress or pinch the previously formed ridges, resulting in a final corrugated tube having an outside diameter greater than the outside diameter of the tube originally fed into the corrugating machine.

3 Claims, 2 Drawing Figures 1 APPARATUS FOR MAKING SPIRAL CORRUGATIONS This invention relates to corrugated. metal tubes. More particularly, this invention is a new and improved machine for forming a corrugated flexible metal tube having an outside diameter greater than the outside diameter of the tube from which the corrugated tube is formed.

With the ever-increasing demand for corrugated tubes, there is an increasing pressure on the industry to increase the rate at which corrugated tubes may be made. At one time, inside mandrels wereused on the inside of the tube to be corrugated. However, the inside mandrels, along with other complicated parts of the machines, did not permit fast formation of the corrugations. This was because the mandrel limits the length of the tube and, among other things, requires bulkier machinery because there is more to revolve.

There are other'systems for making corrugated tubing without using a central mandrel to support the tube. Some of these systems provide a flexible tube having an outside diameter greater than the outside diameter of ing machines. Also, with my new machine no mandrel is required and exceptionally long tubing can be fed to the machine at a much faster rate than can be done with other known tube corrugating machines.

Briefly described, my new apparatus comprises at 1 least two indenting members. Both of the indenting members are adapted to perform a'pinching effect on previously formed ridges, and also adapted to increase the outside diameter of the tube.

The invention, as well as its many advantages, may be further understood by reference to the following detailed description and drawings in which:

FIG. 1 is a sectional view of my new invention; and

FIG. 2 is a sectional view, on an enlarged scale, of a portion of the machine of FIG. 1.

Referring to the Figures, the tube corrugator includes a-cup-shaped housing 10. The housing may be connected directly to an engine lathe spindle face plate (not shown) or any similiar heavy-duty spindle (not shown) to provide rotation to the housing about the tube. The housing is also movable laterally. In order to permit lateral movement of the housing, a large inlet bore 14 and a large outlet bore 16 are provided in the tube inlet and outlet portions of the movable housing 10, respectively.

Mounted within the housing 10 are three ball bearings 18, 20, and 22. The ball bearings provide for the free rotation of the annular indenting heads 24, 26, and 28 at an rpm different fro housing 10. The indenting heads extend from annular rings 30, 32, and 34, respectively, which in turn are connected, by screws 36,

38, and 40, respectively, to ring supports 42, 44, and 65 46, respectively.

The tube 12 is fed into the inlet thimble 48, Supported by tubular thimble support 50. The finished cormember to contact the tube 12 to form the grooves 56 and ridges 58. As the tube is pulled through the housing 10, annular indentingheads 26 and 28 perform a pinching effect on the ridges 58 to form the final corrugated tube, having ridges 60 and grooves 62- (see FIG. 2).

The indenting heads 24 and 26 have the same shape and are tilted to form the same angle such as angle A shown in FIG. 2 with respect to a plane normal to the tube axis. This angle is chosen to produce the desired corrugation helix. The indenting head 28 is thinner than the other two indenting heads, and forms a smaller angle with a plane normal to the tube axis than the angle B formed by the indenting heads 24 and 26. This angle also is chosen to produce the desired corrugation helix and ridge 60 thickness. I

The pinching effect of indenting heads 26 and 28 is more clearly shown in FIG. 2. Note that the ridges 60 are longer and thinner than the ridges 58, thus providing a final corrugated tube 61 which has a larger outside diameter than the outside diameter of the tube 12 (FIG. 1). Note, however, that the grooves 62 are shallow enough that the inside diameter of the tube has not been decreased when compared with the grooves 56. Thus, the strength of the final corrugatedtube is maintained, even though its outside diameter has been increased.

Referring to FIG. 1, the housing 10 is shown in its laterally displaced position, so that indenting heads 24, 26,'and 28 are in contact with the outside of the tube. After the complete tube has been corrugated, the housing 10 is moved upwardly, looking at FIG. 1, to disengage the indenting heads 24, 26 and 28 from the tube. All three indenting heads contact the outside of the tube at the same circumferential position on the outside of the tube.

In operation, the tube 12 is fed through housing 10. Indenting head 24 begins the formation of grooves 56 and ridges 58. As the tube is drawn through housing 10 by its threading action, it engages the indenting head 26 and almost immediately engages indenting head 28. Indenting head 26 completes the formation of grooves 56 and ridges 58 and, in cooperation with indenting head 28, performs a pinching effect on ridges 58 to form the final corrugated tube having ridges 60 and grooves 62. The ridges 60 are narrower than ridges 58, and provide a tubing having a greater outside diameter than the tube from which it is formed.

I claim:

1. An apparatus for corrugating a thin-rolled tube comprising: a first indenting member freely rotatably mounted in a housing so as to engage the outside perimeter of the tube at an angle with respect to a plane normal to the tube axis; and

a second indenting member which is thinner than the first indenting member freely rotatably mounted in the housing to angularly engage the outside of the tube at an angle with respect to a plane normal to the tube axis which is less than the angle of engagement of the first indenting member. 2. An apparatus for forming corrugations on the outside of a thin-walled metal tube comprising:

a first freely rotatable indenting member; a second freely rotatable indenting member;

a third freely rotatable indenting member; and

means for feeding the tube past the three indenting members, the first indenting member being in contact with the tube to begin the formation of corrugations, the second indenting member being longitudinally spaced from the first indenting member and having the same shape as said first indenting member to continue the formation of the corrugations, and said third indenting member being separated from the second indenting member a distance equal to the desired pitch of the corrugations, the angular contacts of the first two indenting members being equal, and the angular contact of the third indenting member being less than the angular l the three indenting members are adapted to contact the outside of the tube at the same circumferential position on the outside of the tube. 

1. An apparatus for corrugating a thin-rolled tube comprising: a first indenting member freely rotatably mounted in a housing so as to engage the outside perimeter of the tube at an angle with respect to a plane normal to the tube axis; and a second indenting member which is thinner than the first indenting member freely rotatably mounted in the housing to angularly engage the outside of the tube at an angle with respect to a plane normal to the tube axis which is less than the angle of engagement of the first indenting member.
 2. An apparatus for forming corrugations on the outside of a thin-walled metal tube comprising: a first freely rotatable indenting member; a second freely rotatable indenting member; a third freely rotatable indenting member; and means for feeding the tube past the three indenting members, the first indenting member being in contact with the tube to begin the formation of corrugations, the second indenting member being longitudinally spaced from the first indenting member and having the same shape as said first indenting member to continue the formation of the corrugations, and said third indenting member being Separated from the second indenting member a distance equal to the desired pitch of the corrugations, the angular contacts of the first two indenting members being equal, and the angular contact of the third indenting member being less than the angular contact of the other two indenting members, with said third indenting member being thinner than the first and second indenting members to reduce the pitch of the corrugations and to increase the outside diameter of the tube as the final corrugations are formed by the second and third indenting members.
 3. An apparatus in accordance with claim 2 wherein: the three indenting members are adapted to contact the outside of the tube at the same circumferential position on the outside of the tube. 